An improved insulating performance fabric has a double-knit body, formed with traditional, relatively smooth, outer surfaces, and an inner surface with the form of multiple fabric “bubbles” separated, e.g., by a grid pattern of intersecting grooves. An insulating, double-knit performance fabric of this disclosure may also be found in the form of a garment comprising the insulating, double knit performance fabric, or in the form of fabric article comprising the insulating, double knit performance fabric, etc.